1. Field of the Invention
This invention relates to a coin selecting apparatus used in vending machines, exchanging machines, service devices, etc., and more particularly to improvements to an electronic coin selecting apparatus which determines the kind of a coin electronically.
2. Description of the Related Art
Conventionally, there are a mechanical coin selecting apparatus which discriminates a coin by checking the properties of a coin mechanically and an electronic coin selecting apparatus which senses the properties of a coin electronically and discriminates the coin in accordance with the sensing output. The latter has an enlarged range of applications because its accuracy of discrimination is excellent and it can be miniaturized.
Generally, an electronic coin selecting apparatus includes an oscillation coil disposed on one side of a coin channel and excited by a signal having a predetermined frequency, and a receiving coil disposed on an opposite side and coupled electromagnetically to the oscillation coil whereby the validity and kind of the coin are determined on the basis of an attenuating voltage waveform from the receiving coil generated due to passage of a coin and the coin is discriminated in accordance with the results of the determination. In other words, the fact that the maximum attenuation voltage of an attenuating voltage waveform produced by the receiving coil due to passage of a coin varies depending upon that coin has been noticed. The validity and kind of a coil are determined depending upon whether the attenuating voltage waveform produced by the receiving coil falls in a predetermined range (window) of determination for a maximum attenuation voltage for the corresponding coin to be discriminated.
However, according to this arrangement, with a coin which causes the receiving coil to produce a greatly attenuating voltage waveform, a signal indicative of the determination of a genuine coin will be produced each time the voltage waveform traverses an allowable range for another coin.
With a coin whose voltage waveform attenuates greatly, a plurality of signals indicative of the determination of a genuine coin will be produced by sole depositing of the coin. In order to cope with this situation, a maximum attenuation point sensing circuit is conventionally provided which senses that the attenuating voltage waveform produced by the receiving coil reaches a maximum attenuation point, and the output from the receiving coil is determined synchronously with a peak signal from the sensing circuit.
However, the sensing circuit includes a unit which stores the outputs from the receiving coil sequentially, a unit which detects the output from the receiving coil being reversed and starting to rise, etc., so that it itself is considerably complicated and renders the entire circuit structure very complicated.
Since the peak signal output from the maximum attenuation point sensing circuit is a discontinuous signal which is produced only when the output from the coil attenuates to a maximum degree, the sensing circuit may operate erroneously due to possible noise similar in magnitude to the peak signal and produced at a time other than when the output from the receiving coil attenuates to a maximum degree. Therefore, it is an object of this invention to provide a coin selecting apparatus which is less likely to operate erroneously and has a simple structure.